Patients are increasingly undergoing more intravascular and minimally invasive procedures as alternatives to open surgical procedures. In particular, needle biopsy procedures are favored over open biopsy procedures if feasible. Less invasive procedures employ a variety of catheters or other devices which are positioned in vascular, abdominal, pulmonary, or urologic spaces with the goal of manipulating, cutting, and/or stabilizing structures at a distance from the operator. A variety of tissue retrieval and biopsy devices or needles are employed to recover tissue samples for analysis. As every procedure has a certain failure rate, there will be by definition cases or instances where a component of the device separates and is difficult to retrieve or a material is placed or separates from a device and needs to be captured and removed. In addition there will be instances in which standard biopsy devices return inadequate amounts of poorly preserved tissue limiting accurate pathologic interpretation.
In the setting of vascular procedures, a catheter segment, wire or balloon segment may become dislodged and must be recovered. In the setting of minimally invasive surgical procedures, a device component, suture clip, or staple, may be lodged in a small cavity or region where retrieval might be compromised or difficult with typical minimally invasive surgical devices. Percutaneous or laparascopic biopsy procedures may be compromised by the recovery of small tissue samples if the capturing or cutting mechanism performs poorly. Occasionally no sample is recovered if the capturing mechanism completely fails. In the practice of biliary endoscopy and urology, stents and other catheters or other dislodged components may require subsequent retrieval.
Retrieval of retained device elements or materials through open direct explorations, can be overly invasive and traumatic, and inconsistent with the basic principles of reducing direct trauma through minimally invasive procedures. Therefore, minimally invasive devices and techniques have been developed to retrieve unintentionally dislodged objects from the body.
Moreover certain pathologic materials, such as thrombi, emboli or stone excrescences, can be difficult to capture within delicate small spaces and require devices that can easily and efficiently capture or grab them for retrieval. The recoverability of a biopsy specimen may highly depend on the mechanical characteristic of the tissue that is being biopsied. The use of retrieval devices for the removal of stones within ureters, or bladder or within the biliary system are examples of the application of retrieval devices to remove pathologic materials that previously required open procedures, which often were associated with significant morbidities.
The development of stones within the ureters can result in renal insufficiency and recurrent infections. Removal of the stones can reverse obstructive phenomena, decrease pain, improve renal function and decrease recurrent infections. Biliary stones dislodged from the gallbladder can result in recurrent biliary obstruction, jaundice, pain and infection which can be alleviated by removal of the obstructing stone elements.
The development of a thrombus or dislodgment of an embolus within a vascular space results in downstream ischemia which can have profound physiologic consequences. If such an event occurs within the central nervous system, focal brain ischemia ensues resulting in the clinical manifestations of a stroke. The development of a thrombus or the dislodgment of an embolus into the peripheral vasculature can result in limb ischemia. Thrombi that develop in the coronary arteries result in myocardial infarctions.
Recovery of tissue specimens through the use of retrieval devices such as percutaneous, endoscopic or laparoscopic specimen capturing biopsy needles, provides critical information that guides treatment decisions. Efficient recovery of adequate amounts of tissue is required for pathologists to render reliable histopathologic diagnoses.
Retrieval devices have been developed and employed for the recovery of tissue specimens, vascular thrombi, or emboli. The process of removing a tissue specimen is referred to as a biopsy procedure. The procedure that removes a thrombosis is called an embolectomy and has been used by Interventional Radiologists and Vascular surgeons therapeutically, for sometime. Removing these thrombi or emboli with minimally invasive procedures can be efficient and potentially less morbid then open direct procedures. Therefore, retrieval devices designed to remove a variety of foreign bodies and tissue components have been developed and are routinely employed in the practice of medicine. Addressing design aspects of the retrieval mechanisms can increase the performance of the devices and provide clinicians with better tools for more reliably retrieving foreign bodies emboli and diagnostic tissue specimens.
A number of foreign body retrieval devices have been designed and have entered the commercial marketplace. While a number of different devices are available, there are generally four types of foreign body retrieval devices that have gained more widespread popularity and use. In particular, the four types of devices can be referred to and identified as the (1) Gooseneck design snare; (2) Texan snare; (3) En Snare; and (4) the In Time retrieval device.
A review of some of the more common prior art devices reveals that the devices can be divided into three designs categories. The first type of design is a device that incorporates single snare or multiple looped snares that project from a catheter. The diameter of the snare loop or loops is controlled by advancing or retracting the catheter “over” the looped wire system or alternatively by advancing or retracting the wire system within a relatively stationary catheter system. The wire loop or loops are manipulated or stabilized by the operator by a long wire which is connected to the loop or snare and extends distally to the proximal portion of a catheter system. Examples of this type of system include the Amplatz gooseneck system or the En Snare system marketed by Merit.
The second type of design includes a mesh or basket assembly which is defined by multiple loops or struts that can be deployed through a catheter system. The basket or mesh system is attached to a wire which extends through the catheter system. The proximal aspect of the wire is available to the operator at the proximal portion of the catheter. The geometry and therefore activation of a mesh system is controlled by varying the relative positions of the catheter meshed/wired structure. In some sense the relationship and control of the geometry of the wire loops is similar to the first type of device in that a catheter initially constrains and keeps the wire mesh system from expanding as it is retained within the catheter lumen. Once the basket or mesh system is advanced through the catheter, it may expand to its fully deployed geometry.
After engaging a foreign body, the basket or mesh system can be retrieved by uniformly pulling back on the wire and catheter without changing the longitudinal relationship of the two components, hopefully with the foreign body engaged. Alternatively, the deployment catheter can be partially pushed over the mesh system to change the geometry of the system and to produce a capturing force along the surface of the foreign body. After such a maneuver, the longitudinal relationship of the activated mesh system and catheter are maintained and the system is removed hopefully with the foreign body securely captured.
A third type of device incorporates a multi-wired basket-like structure located at the end of a catheter system. The In Time retrieval system marketed by Boston Scientific is an example of this type of system. A wire mesh or multi-strutted system is attached to the tip of a microcatheter. The mesh or basket element is not designed to be deployed from within the catheter system but is attached to its most distal end. The geometry of the mesh capturing system is controlled by a core wire that passes through the catheter system and attaches to the distal aspect of the mesh or basket system. The capturing element is “opened up” that is the spaces between the wires or struts are increased by decreasing the longitudinal length of the basket system by pulling the core wire proximally. Once a foreign body is engaged within the capturing mesh wire system the spaces between the capturing struts can be decreased by elongating the wire system by advancing the core wire forward or distally. The mesh system can also be rotated by rotating the core wire, sometimes increasing the device's ability to capture a foreign body. More specifically, the In Time product is made of a Nitinol braided microcatheter shaft, a radiopaque retrieval basket and a steerable Nitinol core wire.
There are a number of shortcomings in the design of the above-described conventional devices and their application in clinical practice, which limits their effectiveness and/or simplicity.
The success of the retrieval procedure depends on the ability of the retrieval device to efficiently and reliably capture the foreign material. The initial steps of the procedure require that the retrieval device must come in contact with the foreign material in a way that allows the device to engage it or grab it. The efficiency of that step depends on the ability of the operator to control the position and contour of the wires/mesh in relation to the foreign material. The design of the first type of retrieval devices makes it difficult to change the contour or geometry of the snare loop since manipulation of a wire at the proximal end of the catheter system must be translated into contour changes of the loop(s) at the distal end of the device. Rotating the internal wire at the proximal end of the catheter may not efficiently translate into controllable movements of the snare loop that will precisely localize the loop into a position adjacent to a foreign material.
As regards, the second or third types of foreign body retrieval devices in which the capturing element is a mesh or basket-like configuration, individual control of any particular wire loop within the mesh is more problematic. The mesh system provides multiple “openings” through which a material potentially will be engaged. However, the fact that there is an increased number of notches or gaps in which a foreign material may enter only increases the probability that such an event will occur and does not guarantee it. The engagement is a relatively chance event and not necessarily driven by a precise alignment and control of a wire loop(s) in the region of the foreign material. Also some of these designs depend on converting longitudinal translation of the core wire into the precise localization of a wire or multiple wires which can be technically challenging.
The ability to engage a foreign material and capture it within the central portion of the basket structure can be compromised by the complicated woven structure of the basket wires which may impede transit and positioning of the foreign material within the basket's central portion.
The ability of the foreign material to remain securely engaged with the retrieval device depends not only on the force to which the material is exposed but the surface area of the grabbing or engaging element which is in contact with the foreign material.
The first type of device generally has one or a few snare loops that engage the foreign material. When the loop size is decreased, the foreign material is pushed against either the tip or distal side of the catheter. Although bringing the foreign material adjacent to the side of the catheter increases the surface area that can contact the material, this type of orientation usually only applies to devices with a single capturing loop and the precision and geometry of engagement may not maximize the amount of surface area that comes into contact with the foreign material.
In devices that are either of the second or third types the surface area of engagement is limited to the surface area described by one or multiple relatively small diameter wires. If a foreign material is engaged between two wires, there will be minimal surface area in contact with the foreign material thereby compromising the reliability of the capture. Of course, if the foreign material finds its way into multiple notches or gaps, the total contact surface area will increase and the engagement will be more secure. However the second possibility may only occur by chance, since as above, it is difficult to precisely direct such a mesh element to engage a foreign material at multiple sites.
Although these types of devices can be useful in certain applications, other devices that maximize their ability to precisely, efficiently capture foreign and pathologic objects as well as tissue samples may be more useful to the interventionalist.
Tissue specimen retrieval devices, often referred to as biopsy needles, are configured to retrieve a representative specimen of tissue for pathologic analysis. Tissue specimens also may be used for immunohistochemical studies as well as molecular evaluations. It is therefore important to recover substantial specimens that are representative of the structure and morphology of the underlying tissue. Most biopsy needles are tubes that are designed to retrieve the specimen within the lumen of the device. The earliest designs included no ancillary mechanisms to capture the specimen once it entered the lumen of the needle. Later designs have incorporated capturing mechanisms to secure the specimen in the lumen to help ensure that an adequate specimen is recovered.
Two types of designs have been employed in soft tissue biopsy needle devices to facilitate the consistent retrieval of adequate specimens. One design includes opposing curved plates that function as a pinching or “biting” mechanism to cut a small segment of tissue which is retained within the opposed plates until they are mechanically unopposed freeing the specimen for recovery. The second design, which is commonly employed, in the great majority of soft tissue biopsy needles, includes a shaft into which a tissue component prolapses and then is cut for retrieval by a biopsy needle tube. The construction is commonly referred to as a “true cut” biopsy needle.
Each of these designs has there disadvantages. Biopsy needles which employ a biting mechanism to secure the specimen for retrieval usually provide limited samples for histopathologic evaluation which sometimes compromises the pathologist's ability to provide the clinician with a definitive diagnosis. Alternatively, the “true cut” design may provide a less than representative tissue sample since the tissue capturing mechanism, by definition, does not provide a full core of tissue.
Newer soft tissue biopsy needles have focused on providing specimen capturing designs that acquire substantial amounts of specimens to maximize the pathologist's ability to render a definitive diagnosis. These soft tissue biopsy needles are designed to capture a full core of a specimen. One such needle is marketed as the BioPince device. It incorporates a flexible component that severs the specimen at the needle tip and retains it within the lumen of the needle to facilitate recovery of the specimen.
Another specimen capturing technology that may be applicable to the construction and design of tissue biopsy needles is the Snarecoil technology. Snarecoils have generally been configured as helical coils whose diameters are reduced by rotation. As the diameter of these capturing coils is reduced they secure a sample in the lumen of a biopsy needle.
The present applicant has a number of issued patents that are directed to various snarecoil designs. For example, snarecoil designs are disclosed in U.S. Pat. Nos. 7,621,923; 7,608,049; 7,608,048; 7,455,645; 7,384,400; 7,338,456; 7,278,970; 6,015,391; 5,634,473; and 5,522,398, each of which is hereby incorporated by reference in its entirety. While these snarecoil designs perform their intended functions, there is a need in particular settings for a different snarecoil design that is more particularly suited for grasping, cutting or deforming certain tissues that tend to collapse when pressure is applied by a conventional snarecoil.
The reduction in the diameter of presently available Snarecoil designs/configurations is limited since many rotations of the coil assembly is required to reduce the diameter of the coil configuration to a minimum. In addition the helical design, by definition, does not cause the coil to pass through the central position of the lumen of the biopsy needle. Since soft tissue capturing coil assemblies must be capable of completely reducing their diameters and/or transecting the central portion of the needle lumen, needle performance is compromised when helical snarecoil capturing mechanisms are incorporated into soft tissue biopsy needles. As a result, in practice, soft tissue biopsy needles that contain helical Snarecoil capturing assemblies do not capture and recover specimens in a consistent fashion. Therefore, to overcome these deficiencies new capturing mechanism designs have been devised.
Other features and advantages of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.